150 fs Cross-Gain Modulation Experiments on Semiconductor Optical Amplifiers

Abstract

Ultrafast gain dynamics in semiconductor optical amplifiers (SOA’s) is of great interest because of the potential application of SOA’s in high-speed optical networks. It also enables to get a better understanding of the fundamental physical processes involved in the interaction between a short optical pulse and a high density plasma. So far, the ultrafast gain dynamics in SOA’s has been mainly studied by means of standard pump and probe (P&P) measurements in which the wavelengths of the pump and probe are identical. Here, we present a new experimental technique which is an ultrafast cross-gain modulation (XGM) between a 150 fs pump pulse and a weak cw probe signal. The advantages of the XGM over the P&P technique are two-fold. Firstly, the probe wavelength can be varied and therefore the gain recovery at different wavelengths around the pump wavelength can be obtained. Secondly, the probe signal is a cw signal, thus having a very narrow linewidth and hence a high spectral resolution. Consequently, information is obtained on the spectral carrier population distribution and its recovery.